Muffler with semi-chambers formed by reduced shell portions



E. G. STRAW 3,371,744

March 5, 1968 v I MUFFLER WITH SEMI-CHAMBERS FORMED BY REDUCED SHELL PORTIONS Filed March 5, 1965 INVENTOR. F/dfaa a 52 /4144 vfliw United States Patent MUFFLER WITH SEMI-CHAMBERS FORMED BY REDUCED SHELL PORTIONS Eldred G. Straw, Grass Lake, Mich assignor to Walker Manufacturing Company, Racine,-Wis., a corporation of Delaware Filed Mar. 5, H65, Ser. No. 437,428

2 Claims. (Cl. 181-61) ABSTRACT OF THE DISCLOSURE A muffler shell is strengthened and made effective as a silencing device by pinching sections together to form a sereis of inwardly extending embossments.

This invention relates generally to exhaust systems for internal combustion engines, and more particularly, to an improved silencing component or muffler construction for use in silencing the exhaust gases.

It is a general object of the present invention to provide a silencing construction of an extremely simple and readily manufactured design.

It is a more particular object of the present invention to provide a silencing construction comprising a plurality of inwardly projecting embossments or pinched sections formed in an outer shell and serving to stiffen the shell and reduce shell noise.

It is another object of the present invention to provide a construction of the above form wherein the inwardly projecting embossments or pinched sections serve to broaden the sound attenuating range of the silencing component by providing attenuate of high frequencies and by providing a low and high frequency interference effect.

Other objects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawing, wherein:

FIGURE 1 is a longitudinal cross-sectional view, partially bro-ken away, of a preferred embodiment of the muffler construction of the present invention;

FIGURE 2 is a transverse cross-sectional view taken along the line 2-2 of FIGURE 1; and

FIGURE 3 is a transverse cross-sectional view of the muffler construction illustrated in FIGURE 1, taken along the line 3-3 thereof.

The silencing component has an elongated hollow cylindrical muffler housing or shell 12 which may be of any desired length. If desired, there may be a hollow cylindrical exhaust gas flow tube or conduit 14 to extend coaxially in the housing 12 and it may be supported therein by suitable means such as the mounting of its ends in reduced diameter gas inlet and outlet bushings 16 and 18 at opposite ends of the housing 12.. The tube 14 is preferably perforated, as by means of louvers 20, to provide communication between the interior of the tube 14 and an annular chamber 22 defined by the inner periphery of the housing 12 and the outer periphery of the tube 14. It is apparent that gas flows straight through the unit 10 in the tube 14 and that the bushings 16 and 18 are connected in an exhaust system in a suitable manner.

In accordance with the principles of the present invention, the housing 12 is formed with a series of longitudinally spaced embossed or pinched down sections, two of which sections are illustrated in FIGURE 1 and designated by the numeral 24. In particular, each of the sections 24 comprise four equally circumferentially spaced indented portions, generally designated 26, that are formed around the housing 12, the excess material between each adjacent pair of the indented portions 26 being gathered into one of four generally U-shaped folds or ridges 28 which are of the same diameter as the housing 12 and extend substantially parallel to the longitudinal axis thereof. As best seen in FIGURE 2, the indented portions 26 project radially inwardly within the chamber 22 to a position approximately midway between the inner periphery of the housing 12 and the outer periphery of the tube 14. They therefore divide the large chamber 22 into a series of connected, smaller semi-chambers.

The indented sections 24 serve to reduce and control shell noise by rigidifying the outer shell 10. They also broaden and increase the sound attenuating effect of the construction by providing for interference and intermixing of low and high frequencies and by providing a combined chamber effect. The chamber 22 in combination with the perforated tube 14 acts as a low frequency attenuator. The sections 24 tend to provide the effect of a series of smaller, higher frequency attenuating chambers, Without any substantial adverse effect on the silencing of the lower frequencies.

Acoustic advantages are obtained with this construction even if the tube 14 is omitted or if it extends over only part of the length of the outer shell 12. Shell noise reduction is still obtained and the sections 24 will then act to provide a series of small (high frequency attenuating) expansion chambers in combination with a large fiow frequency attenuating expansion chamber. In this case the outer shell 12 will define the gas flow passage and the sections 24 will provide interference and intermixing of the gases as well as slight restrictive effects that promote sound attenuation. I

Modifications may be made Without departing from the spirit and scope of the invention.

I claim:

1. In an exhaust gas silencing construction, an elongated hollow cylindrical shell defining an elongated sound attenuating chamber for relatively low frequencies, and a plurality of reduced diameter sections formed in said shell and extending radially inwardly a distance materially less than the radius of said shell and dividing said chamber into a plurality of interconnected semi-chambers for attenuating lower frequencies than said elongated chamber, said reduced diameter sections each comprising a plurality of portions separated and connected to each other by U-shaped folds in the shell which extend radially outwardly from the section.

2. In a muffler construction, a hollow cylindrical muflier housing, an elongated gas flow tube extending coaxial-1y through said housing, said tube and said housing defining an annular chamber therebetween, said housing being formed with four reduced diameter sections which project radially inwardly into said chamber and are separated by U-shaped folds, said sections being equally circumferentially spaced around a series of longitudinally spaced circumferential portions of said housing and extending only part way from the housing to the tube.

References Cited UNITED STATES PATENTS 1,777,489 10/1930 Hamilton 18161 XR 2,241,768 5/1941 Dererner 18161 2,3 67,753 1 1945 Buck. 3,263,772 8/1966 Irwin et all.

FOREIGN PATENTS 258,890 6/1928 Italy.

OBERT 5; WARD, JR., Primary Examiner. 

